The present invention describes a paste with application as a try-in paste (i.e., trial paste) useful for assisting in the determination of the correct choice of a dental cement used to apply a dental prosthesis to a tooth.
Try-in pastes (i.e., trial pastes) are used in assisting a dentist in the selection of an appropriate dental cement for bonding a dental prosthesis (e.g., veneer, in-lay, on-lay, etc.), which is often translucent, to a tooth. This selection depends on the optical properties of the final polymerized cement and the dental prosthesis compared to the optical properties of the other teeth of the patient.
Typically, a try-in paste, which is matched to a dental cement with respect to optical properties (often just color-matched), is used to apply temporarily the dental prosthesis to a prepared tooth surface. The dentist determines if the optical properties (at least color) would be esthetically desirable for the combination of the prosthesis and underlying cement. If so, the prosthesis is removed and try-in paste is washed away and the appropriately matched dental cement is used to apply the prosthesis. If not, the prosthesis is removed and try-in paste is washed away and this is repeated with a different try-in paste appropriately matched to a different dental cement.
Traditionally, such try-in pastes are based on glycerin. They typically either have poor handling characteristics or leave a residue after water cleanup. Additionally, because glycerin is transparent optically, some difficulty is encountered in preparing pastes whose optical properties closely match those of the polymerized cement. Thus, additional try-in pastes are desired that are capable of better shade matching.
The present invention provides a try-in paste (i.e., trial paste) suitable for shade matching to a corresponding polymerized dental cement, so that a dental cement of the correct shade can be selected for bonding a dental prosthesis to a tooth of a patient. As used herein, xe2x80x9cshade matchingxe2x80x9d refers to the use of a try-in paste for guiding a dentist in the selection of a shade-matched dental cement for use in bonding a dental prosthesis to a tooth of a patient. The selection of an appropriate dental cement shade depends on the optical properties (typically, color, and preferably, color and opacity) of the polymerized cement and the dental prosthesis compared to the optical properties of the other teeth of the patient.
In a preferred embodiment, the present invention provides try-in paste that includes: a polyalkylene glycol that is liquid at room temperature; a polyalkylene glycol that is solid at room temperature; and particulate material; wherein the polyalkylene glycols are present in amounts to provide a paste having a consistency of about 20 mm to about 50 mm; and wherein the particulate material is present in an amount to provide a try-in paste having a shading (i.e., shade) that matches the shading of a corresponding polymerized dental cement.
Preferably, the shading match includes a color match, and more preferably, a color match and an opacity match. That is, for particularly preferred embodiments, particulate material is present in an amount to provide a try-in paste having a color and opacity that matches the color and opacity of a corresponding polymerized dental cement. Preferably, the color match is within a Delta E* of three units or less. Preferably, the shading match is within a Delta CR of five units or less.
Preferably, the polyalkylene glycols are polyethylene glycols. Preferably, the liquid polyethylene glycol has a weight average molecular weight of about 100 g/mol to about 600 g/mol and the solid polyethylene glycol has a weight average molecular weight of about 700 g/mol to about 20,000 g/mol. Preferably, the ratio of liquid to solid PEG is within a range of about 1/1 to about 10/1, and more preferably, about 2/1 to about 5/1.
In another preferred embodiment, the present invention provides a kit for selecting a dental cement for bonding a dental prosthesis to a tooth of a patient. The kit includes: a dental cement; and a corresponding try-in paste, wherein the try-in paste is as described above. The kit typically and preferably includes more than one try-in paste and their corresponding cements. The try-in paste includes particulate material in an amount to provide a try-in paste having a shading that matches the shading of a corresponding polymerized dental cement. Preferably, the shading match between the try-in paste and the corresponding polymerized dental cement includes a color match and an opacity match. Preferably, the color match is within a Delta E* of three units or less. Preferably, the opacity match is within a Delta CR of five units or less.
Another preferred kit includes a dental cement and a corresponding try-in paste, wherein the try-in paste includes: a polyethylene glycol that is liquid at room temperature and has a weight average molecular weight of about 100 g/mol to about 600 g/mol; a polyethylene glycol that is solid at room temperature and has a weight average molecular weight of about 700 g/mol to about 20,000 g/mol; and particulate material that includes a pigment and an optional filler; wherein the polyethylene glycols are present in amounts to provide a paste having a consistency of about 20 mm to about 50 mm; wherein the particulate material is present in an amount to provide a try-in paste having a shading that matches the shading of a corresponding polymerized dental cement.
The present invention also provides a method of selecting a dental cement for bonding a dental prosthesis to a tooth of a patient. The method includes: selecting a first try-in paste; applying the dental prosthesis to the tooth of the patient using the first try-in paste; comparing the shading of the dental prosthesis and the first try-in paste to the shading of the other teeth of the patient to determine if there is an appropriate match; removing the first try-in paste; and bonding the dental prosthesis to the tooth using a corresponding dental cement. The try-in paste includes: a polyalkylene glycol that is liquid at room temperature; a polyalkylene glycol that is solid at room temperature; and particulate material; wherein the polyalkylene glycols are present in amounts to provide a paste having a consistency of about 20 mm to about 50 mm; wherein the particulate material is present in an amount to provide a try-in paste having a shading that matches the shading of a corresponding polymerized dental cement. Preferably, comparing the shading includes comparing the color and opacity of the dental prosthesis and the try-in paste to the color and opacity of the other teeth of the patient. Preferably, the method further includes selecting a different try-in paste if the match using the first try-in paste is not appropriate.
This invention provides dental try-in (i.e., trial) pastes that include a mixture of liquid and solid polyalkylene glycols, preferably, polyethylene glycols (PEGs). Such try-in pastes are used to shade match (typically, match the color, and preferably match the color and opacity) of final polymerized dental cements used to apply a dental prosthesis (i.e., restorative such as a veneer, in-lay, on-lay, etc., whether it be made of porcelain, ceramic, or a composite material). The dental cements typically can be resin cements, ionomeric cements, or resin-modified ionomeric cements. Preferably, the present try-in pastes are used to match the optical properties of (meth)acrylate-based resin cements.
Such pastes have a consistency (defined below) such that they are semi-solid. Such properties provide good handling characteristics (e.g., little or no slump). Preferred pastes are homogeneous. Preferred pastes are also shelf-stable such that there are no significant changes in handling, homogeneity, color, or opacity while stored at room temperature in the dark for at least one year, and preferably for at least two years. Alternatively, preferred pastes are stable such that there are no significant changes in handling, homogeneity, color, or opacity while stored overnight in the dark at 37xc2x0 C., and preferably at 45xc2x0 C.
The pastes are preferably removable from a surface (e.g., tooth surface and/or dental prosthesis) under a stream of room temperature water, typically from a dental water-spray unit, within about 10 seconds, such that there is little or no residue remaining.
The try-in pastes of the present invention include one or more particulate materials that give pastes with good handling properties and that have optical properties similar to polymerized dental cements, typically, polymerized methacrylate-based permanent dental resin cements. Typically, the particulate material includes one or more pigment(s) and/or one or more filler(s). Preferably, the particulate material includes one or more pigment(s) and optionally one or more filler(s).
Generally, a single try-in paste has one corresponding dental cement. As used herein, a xe2x80x9ccorrespondingxe2x80x9d try-in paste is one that is appropriately matched to the dental cement with respect to its final polymerized shade (typically, color, and preferably color and opacity).
Preferably, particulate material (preferably, pigment(s) and optional filler(s)) is present in an amount to provide a try-in paste having a color that matches the color of a corresponding polymerized dental cement. As used herein, a color that xe2x80x9cmatchesxe2x80x9d is one that has a very good match between L*, A*, and B* in the CIE color space (described in greater detail in the Examples Section), and preferably demonstrates a Delta E* of three units or less when compared to a corresponding polymerized dental cement.
More preferably, particulate material preferably, pigment(s) and optional filler(s)) is present in an amount to provide a try-in paste having an opacity that matches the opacity of a corresponding polymerized dental cement. As used herein, an opacity (i.e., Contrast Ratio or CR) (described in greater detail in the Examples Section) that xe2x80x9cmatchesxe2x80x9d a polymerized dental cement is one that has a very good CR match, and preferably demonstrates a Delta CR of about five units or less when compared to a corresponding polymerized dental cement.
The pigments may be colored (including black) pigments or white pigments. Preferably, to provide the desired shade match, the total amount of colored pigment used is at least about 0.001 weight percent (wt- %). Preferably, to provide the desired shade match, the total amount of colored pigment(s) used is no greater than about 0.1 wt- %. More preferably, these colored pigments are pure primary colors, i.e., red, yellow, and blue. Those skilled in the art will recognize this difficult challenge is made easier if the pigments are pure or nearly pure primary colors. In addition, a black pigment typically is preferred. Typically, a white pigment can be used in an amount of up to about 5 wtxe2x88x92%. These weight percentages are based on the total weight of the try-in paste.
Suitable pigments are those typically used in dental applications, and are preferably FDA approved. Examples of suitable colored (including black) pigments include the metal oxides such as iron oxides, aluminum oxides, copper oxides, chromium oxides, cobalt oxides, and ruthenium oxides. In addition, mixed metal oxides, i.e., spinels, and metal salts can be utilized as potentially suitable pigments. The preferred white pigments are the oxides of titanium.
Preferably, to provide the desired handling properties and shade match, the total amount of filler used is at least about 5 wtxe2x88x92%. Typically, to provide the desired handing properties and shade match, the total amount of filler used is no greater than about 50 wtxe2x88x92%, and preferably, no greater than about 20 wtxe2x88x92%. These weight percentages are based on the total weight of the try-in paste.
Suitable fillers are those typically used in dental applications and can be selected from any material suitable for use in medical applications. The fillers can be finely divided and preferably have a maximum particle diameter less than about 50 micrometers and an average particle diameter less than about 10 micrometers. The fillers can have a unimodal or polymodal (e.g., bimodal) particle size distribution. The fillers can be inorganic materials or crosslinked organic materials that are insoluble in the PEG components. Preferred fillers are white or nearly white. If a filler contains, for example, any red, yellow, or blue color, the task of obtaining color and opacity matching is made more difficult.
Suitable inorganic fillers are naturally occurring or synthetic materials such as quartz, nitrides (e.g., silicon nitride), zirconia-silica, glasses derived from, e.g., Ce, Sb, Sn, Zr, Sr, Ba, and Al. Other glasses include colloidal silica, feldspar, borosilicate glass, kaolin, talc, titania, and zinc glasses. Also suitable are the radiopaque, Zrxe2x80x94Si sol-gel fillers such as those described in U.S. Pat. No. 4,503,169 (Randklev) and submicron silica (e.g., pyrogenic silicas such as the AEROSIL series OX 50, 130, 150, and 200 silicas commercially available from Degussa Co., Germany and CAB-O-SIL M5 silica sold by Cabot Corp., Tuscola, Ill.). Optionally, the surface of the filler particles may be treated with a surface treatment, such as a silane coupling agent, as disclosed in U.S. Pat. No. 6,030,606 (Holmes).
Suitable non-reactive organic fillers include filled or unfilled pulverized polycarbonate, polyepoxides, and the like. Mixtures of the non-reactive organic fillers can also be used.
Those skilled in the art will recognize that both fillers and pigments add opacity to the paste formulations and care must be taken in choosing the proper amounts of filler, colored, black, and white pigments to achieve both color and opacity matching. Also, various combinations of fillers and pigments can be used to achieve the desired result.
The try-in (i.e., trial) paste compositions of this invention include a relatively low molecular weight (MW) polyalkylene glycol, preferably a polyethylene glycol (PEG), that is liquid at room temperature (i.e., about 20xc2x0 C. to about 25xc2x0 C.) and a higher MW polyalkylene glycol, preferably a polyethylene glycol (PEG) that is solid at room temperature. Suitable polyalkylene glycols include polyethylene glycols, polypropylene glycols, and copolymers thereof. Mixtures of low MW liquid polyalkylene glycols and mixtures of high MW solid polyalkylene glycols can be used if desired. It is envisioned that a low MW polyethylene glycol can be mixed with a high MW polypropylene glycol.
Preferably, suitable liquid PEG""s have a weight average MW of no greater than about 600 grams/mole (g/mol), and more preferably, no greater than about 400 g/mol. Preferably, suitable liquid PEG""s have a weight average MW of at least about 100 g/mol, and more preferably, at least about 200 g/mol. Preferably, suitable solid PEG""s have a weight average MW of at least about 700 g/mol, more preferably, at least about 1,000 g/mol, and most preferably, at least about 1,400 g/mol. Preferably, suitable solid PEG""s have a weight average MW of no greater than about 20,000 g/mol, and more preferably, no greater than about 4,000 g/mol.
The ratio of liquid PEG and solid PEG is selected to provide a paste having the desired handling characteristics, as evidenced by a consistency of about 20 millimeters (mm) to about 50 mm as defined by the consistency test specified in ISO 4049 xe2x80x9cResin-based Dental Luting Materialxe2x80x9d, Third Edition, published Jul. 15, 2000. Consistencies thicker than about 20 mm suffer from difficulty in dispensing and poor handling properties while consistencies thinner than about 50 mm suffer from excessive slump and runniness and an inability to hold a dental prosthesis in place for visual inspection.
Typically, the desired ratio for any one formulation depends on the particular MW of the liquid and solid PEG""s. This can be determined by one of skill in the art without undue experimentation. In general, a weight ratio of liquid to solid PEG of at least about 1/1 is preferred, with a ratio of at least about 2/1 being more preferred. Also, a weight ratio of liquid to solid PEG of no greater than about 10/1 is preferred, with a ratio of no greater than about 5/1 being more preferred.
A particularly preferred paste includes a ratio of about 2.0-4.0 parts of a 200-400 MW liquid PEG to about 1.0 part of a 1,400-3,500 MW solid PEG, and more preferably, to about 1.0 part of a 2,000-3,500 MW solid PEG.
Preferably, the mixture of liquid and solid PEG""s is heated until the solid PEG has melted and dissolved in the liquid PEG, and subsequently cooled with mixing. In this way, a creamy, homogeneous paste is typically obtained. If the heated mixture is cooled without mixing, a dispersion of solidified particles of high MW PEG in liquid PEG may be obtained. Pastes of this type are not suitably homogeneous, i.e., the naked eye can identify individual particles of solidified high MW PEG in a liquid low MW PEG.
Subsequent to the cooling cycle, fillers and/or pigments can be added to give a match between the shade (e.g., color and opacity) of the try-in paste and a final polymerized cement conventionally used in bonding a dental prosthesis. It is generally desirable to use pigments and fillers, if used, of a type that are similar to the cement being matched. In general, a color difference, Delta E*, of three units or less is considered to be an excellent match and difficult to discern a color difference.
The Examples Section describes six different try-in paste formulations (Trial Pastes A-F) and six different cement formulations (Cements A-F) corresponding to the same shade. Table 3 shows the computer results of the shade match obtained between the try-in pastes and their corresponding polymerized cements with color comparisons reported as Delta E* and opacity comparisons reported as Delta CR. These results are significantly better than many other conventional bonding systems, which can have Delta E* values of 12 and higher for some colors.
The present invention also provides a kit for selecting a dental cement for bonding a dental prosthesis to a tooth of a patient. The kit includes one or more dental cements and one or more try-in pastes of the present invention, wherein each dental cement has a corresponding shade-matched try-in paste. Typically, there is a translucent shade for use where the prosthesis provides the desired esthetics and no color shifting is necessary. If masking or shade adjustment is required, several other shades of try-in pastes and cements can be provided, including white, yellow, and dark shades. The kit will often also include a syringe that allows for easy and direct placement of the paste onto the prosthesis.
The dental cements can be resin cements, ionomeric cements, or resin-modified ionomeric cements. Preferably, the present try-in pastes are used to match the optical properties of (meth)acrylate-based resin cement. Suitable examples include a cement commercially available under the trade designations 3M ESPE RelyX Veneer Cement (3M Co., St. Paul, Minn.), CALIBRA (Dentsply, York, Pa.), VARIOLINK II (Ivoclar Vivadent, Amherst, N.Y.), and NEXUS (Kerr, Orange, Calif.).
The present invention also provides a method of selecting a dental cement for bonding a dental prosthesis to a tooth of a patient. The method includes: selecting a first try-in paste; applying the dental prosthesis to the tooth of the patient using the first try-in paste; comparing the shade of the dental prosthesis and the first try-in paste to the shade of the other teeth of the patient to determine if there is an appropriate shade match; removing the first try-in paste; and bonding the dental prosthesis to the tooth using a corresponding dental cement. As used herein, an xe2x80x9cappropriate matchxe2x80x9d between the prosthesis/try-in paste and the other teeth of the patient occurs upon visual inspection and is defined as an esthetic result that is acceptable to the patient and dentist.
Comparing the shade includes comparing the color of the dental prosthesis and try-in paste to the color of the other teeth of the patient. Preferably, comparing the shade also includes comparing the opacity of the dental prosthesis and try-in paste to the opacity of the other teeth of the patient. Preferably, the method further includes selecting a different try-in paste if the shade match using the first try-in paste is not appropriate. This can be repeated numerous times until the appropriate shade match between the try-in paste and overlying prosthesis with the other teeth of the patient is obtained.